This invention relates to continuous tape having an adhesive on one surface, useful for sealing boxes or the like.
Conventional adhesive tape is generally manufactured by applying a coating of a pressure sensitive adhesive material onto a continuous web or substrate. Adhesive tapes suitable for sealing boxes are often made with polypropylene as the web or substrate and a thin, smooth, continuous coating of an adhesive such as an acrylic polymer resin. Such pressure-sensitive acrylic resin adhesive tapes are preferred for box sealing applications since they exhibit good adhesive performance over a wide range of temperatures.
An improved sealing tape is disclosed in U.S. Pat. No. 5,366,775 of Kao which discloses an easy peel tape of an adhesive on a thin film plastic, e.g., polypropylene, with a release coating and center strip that is adhesive free to facilitate tape removal from the tape roll. U.S. Pat. No. 2,819,180 of Koenig discloses a specialty self-adhesive tape intended for reinforcing holes in paper made by tab punchers; the tape uses an India rubber adhesive on polyvinylchloride film. The tape has several features that minimize processing problems in tab punching equipment, including narrow point indentations for preventing continuous surface contact of adjacent layers in the wound roll and also a non-adhesive middle zone and narrow non-adhesive edge zones where the tape is guided by the tab punching equipment.
Sealing tape used for commercial applications such as box sealing is generally used in large quantities, so economical sealing tape grades are highly desired. Since the adhesive component of the tape constitutes a significant portion of the total cost of the materials employed in manufacturing adhesive tape, there is incentive to minimize the amount of adhesive coating employed, provided that the desired adhesive properties are not compromised. One approach used to this end is reducing the thickness of the adhesive coating. It has been found that adhesive tapes using pressure-sensitive adhesives such as acrylic resins require a minimum of about 0.7 mil (1 mil equals 0.001 inch or 0.025 mm) thickness of coating in order to provide acceptable adhesive sealing properties. Below about 0.7 mil (about 0.018 mm) thickness, the adhesive coating no longer provides the degree of tackiness required for satisfactory box sealing performance.
The present invention addresses the need for an improved economy grade of adhesive tape that provides good box sealing performance.